RENO, Nev.  The threat of being eaten could drive the march of Mormon crickets as they munch their way across millions of acres in the arid West, new research suggests.

An international group of researchers has been studying the crickets that have invaded much of Nevada, Utah and Idaho in recent years.

They found that the insects that move in large bands survive on salt and protein found in seeds, flowers, dead animals and feces. But when those food sources are absent, the bugs turn to what's available -- each other. The crickets themselves are "walking packages of protein and salt," the study said.

"We suspect that they also move more because of the chance of being eaten," said Patrick Lorch, a research biologist with Kent State University.

"You can imagine that if you are at the back of a band of 1 million marching crickets, there is little food left and the cricket in front of you starts to look mighty tasty," Lorch told the Reno Gazette-Journal.

Crickets slowed by injury are particularly vulnerable to being eaten by their brethren, researchers found.

Lorch was among researchers from the United States, England and Australia that conducted the study, published recently by the National Academies of Science.

Also known as flightless katydids, Mormon crickets can destroy 40 percent to 50 percent of the vegetation in their path. About 12 million acres were infested by the insects last year in Nevada.

Lorch said it's uncertain whether the danger of being eaten from behind really motivates the crickets at the head of the column to step up the pace. The insects are not cognizant, but the danger could be hard wired into their tiny brains, he said.

"We don't honestly know if they move faster than they would because of the fear of being eaten," Lorch said. "But that's the sort of thing we imagine is going on."